High Comp. Piston

By steiner1984, Posted March 21, 2008

What will a high comp piston affect and how much will it affect it?

By DOIWANTATHUMPER, Posted March 22, 2008

a higher compression motor puts more stress on valve train parts on a 4-stroke and other componenets like bearings, gaskets, seals, etc. in the motor but going from like the early YZ's up to 2007 to the same compression piston that is in the 08 is not a rediculous amount of compression that will really hurt anything... if you plained the head, put a higher compression piston in, and really started to go crazy then the added compression will put even more stress on the motor, how much is unknown and can only be determined by what modifications you perform and measuring before and after...

By myz250f, Posted March 22, 2008

Ah, one thing people always forget is altitude. If you live in utah chances are you don't live at sea level, and don't get 14.7 psi of atmospheric pressure. So, you don't have as much air in the cylender when you begin the compression process, the higher you are the less you start with. If you wan't to go with a high comp. piston, and you live at a higher altitude (3000ft+) then do it. You won't have to worry about race fuel either, just use the premium pump fuel. The engine was designed to opperate at sea level, and can handle the extra compression that most aftermarket pistons provide.

By steiner1984, Posted March 22, 2008

What would a high comp. do as far as power

By ruralrider, Posted March 22, 2008

Ive heard it adds power to the entire power curve, some have said it flattens the top end up a bit but not much. Most everyone says that they notice newfound low end power.

By steiner1984, Posted March 22, 2008

By will-burr, Posted March 22, 2008

By will-burr, Posted March 22, 2008

Oh yeah another thing is that 92 Pump Gas is fine and I have never heard any pinging... I run Chevron gas.

By ruralrider, Posted March 22, 2008

no need to rejet since the bore has not gotten any bigger it will still need the same amount of gas as before. On installation just take your time and make sure you know what you are doing. Get your cylinder honed at a local shop too for proper ring break in.

By myz250f, Posted March 22, 2008

Is it going to be hard to install? Depends on your own mechanical skills, how much time you have, if you have many tools of your own, or maybe a place to work on it. If you have a service manual, a reasonable collection of tools and a GOOD torque wrench, then you should have no problem doing the mod yourself, as long as you have space to work in and you aren't pressed for time. When doing something like this for the first time, it's always a good idea to have all of your parts spread out and organized to keep the confussion to a minimum. If you get frustrated step back, cool off and try again. Good luck, and happy wheelis.

By live4yamaha, Posted March 28, 2008

i would like to put a higher comprsion piston in mine but i am afriad it wont be relieable. will it be????